Polymeric fluorescent substance and polymer light-emitting device

ABSTRACT

Provided is a polymeric fluorescent substance showing fluorescence in solid state, which has a specific carrier drift mobility, a specific repeating unit, and specific number-average molecular weight. The polymeric fluorescent substance is excellent in solubility to organic solvents, and has higher efficiency and longer lifetime in applying as a polymer LED.

BACKGROUD OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a polymeric fluorescentsubstance, a polymer light-emitting device (hereinafter, referred to aspolymer LED), and a device using the same.

[0003] 2. Description of the Related Art

[0004] Inorganic electroluminescence devices (hereinafter, sometimesreferred to as inorganic EL device) using an inorganic luminescentmaterial as a light-emitting material are used for example for sheetlight sources as back-lights and displays such as a flat panel displayand the like, however, an alternating current of high voltage has beenrequired for light emission.

[0005] Recently, there has been reported an organic electroluminescencedevice (hereinafter, sometimes referred to as organic EL device) havinga double-layer structure in which an organic fluorescent dye as alight-emitting layer is laminated with an organic charge transportcompound used in photosensitive layer for electrophotography and thelike (Japanese Patent Application Laid-Open (JP-A) No. 59-194393). Sinceorganic EL devices have characteristics that light emissions of a lot ofcolors are obtained easily in addition to low voltage driving and highluminance as compared with inorganic EL devices, there have beenreported a lot of trials regarding device structures, organicfluorescent dyes and organic charge transport compounds of organic ELdevices [Jpn. J. Appl. Phys., 27, L269 (1988), J. Appl. Phys., 65, 3610(1989)].

[0006] Further, apart from organic EL devices using mainly organiccompounds having a lower molecular weight, polymer light-emittingdevices using light-emitting materials having a higher molecular weighthave been proposed in such as WO 9013148 published specification, JP-ANo. 3-244630, Appl. Phys. Lett., 58, 1982 (1991). WO9013148 discloses inthe Examples an EL device using a thin film of poly(p-phenylenevinylene) obtained by forming a film of a soluble precursor on theelectrode and subjecting it to a heat treatment to convert the precursorinto a conjugated polymer.

[0007] Further, JP-A 3-244630 has exemplified a conjugated polymershaving a feature that they are themselves soluble in a solvent and needsno heat treatment. Also in Appl. Phys. Lett., 58, 1982 (1991), apolymeric light-emitting materials soluble in a solvent and a polymerLED fabricated using the same are described.

[0008] Polymer LEDs are advantageous for formation of a film havinglarge area and reduction in cost since an organic layer can be easilyformed by coating with using a polymeric fluorescent substance solublein organic solvents, as compared with the case of vapor deposition of amaterial having a lower molecular weight, and the mechanical strength ofthe resulting film is believed to be high because of a high molecularweight thereof.

[0009] Conventionally, as the light-emitting materials used in thesepolymer LEDs, in addition to the above-described poly(p-phenylenevinylene), there have been reported polyfluorene (Jpn. J. Appl. Phys.,30, L1941 (1991)), poly p-phenylene derivative (Adv. Mater., 4, 36(1992)) and the like.

[0010] In order to utilize the film-formable characteristics of apolymeric fluorescent substance by coating, there have been demanded apolymeric fluorescent substance having excellent solubility in organicsolvents. To realize the practical falt panel display, there have beendemanded a polymer LED having high efficiency and long.

[0011] The object of the present invention is to provide a polymericfluorescent substance having more excellent solubility to organicsolvents, a polymer LED having high performance which can be driven athigh efficiency and longer lifetime using said polymeric fluorescentsubstance.

SUMMARY OF THE INVENTION

[0012] As a result of intensive studies, the present inventors havefound that a polymeric fluorescent substance having a specific carrierdrift mobility and a specific repeating unit is more excellent insolubility to organic solvents, and has higher efficiency and longerlifetime in applying as a polymer LED, and reached to the completion ofthe present invention.

[0013] Namely, the present invention relates to [1] a polymerfluorescent substance which emits fluorescence in solid state, has anumber-average molecular weight in terms of polystyrene of 1×10⁴ to1×10⁸, has at least one repeating unit of the following general formula(1) and in which the ratio of the hole drift mobility μ_(H) to theelectron drift mobility μ_(E) of said polymer fluorescent substance isfrom 0.1 to 10:

[0014] [in the formula, Ar₁ is an arylene group having 6 to 60 carbonatoms contained in the main chain portion or a divalent heterocycliccompound group having 3 to 60 carbon atoms contained in the main chainportion].

[0015] Moreover, the present invention relates to [2] a polymerfluorescent substance which emits fluorescence in solid state, has anumber-average molecular weight in terms of polystyrene of 1×10⁴ to1×10⁸, and has each of the repeating units represented by the formulae(2), (3) and (4):

[0016] [in the formula, Ar₂ is an arylene group having 6 to 60 carbonatoms contained in the main chain portion or a divalent heterocycliccompound group having 3 to 60 carbon atoms contained in the main chainportion],

[0017] [in the formula, Ar₃ is an arylene group having 6 to 60 carbonatoms contained in the main chain portion or a heterocyclic compoundgroup having 3 to 60 carbon atoms contained in the main chain portion.],

[0018] [in the formula, Ar₅ is an arylene group having 6 to 60 carbonatoms contained in the main chain portion or a divalent heterocycliccompound group having 3 to 60 carbon atoms contained in the main chainportion].

[0019] Moreover, the present invention relates to [3] a polymerlight-emitting device comprising at least one light-emitting layercontaining a polymer fluorescent substance, placed between a pair of ananode and a cathode at least one of which is transparent orsemi-transparent, wherein, the light-emitting layer contains a polymerfluorescent substance of above described [1] or [2].

[0020] Further, the present invention relates to [4] a sheet lightsource using a polymer light-emitting device of above described [3].

[0021] Next, the present invention relates to [5] a segment displayapparatus using a polymer light-emitting device of above described [3].

[0022] Next, the present invention relates to [6] a dot matrix displayapparatus using a polymer light-emitting device of above described [3].

[0023] And, the present invention relates to [7] a liquid crystaldisplay apparatus using a polymer light-emitting device of abovedescribed [3].

DETAILED DESCRIPTION OF THE INVENTION

[0024] The polymeric fluorescent substance and a polymer LED using thesame will be described in detail below.

[0025] The polymeric fluorescent substance of the present invention is apolymeric fluorescent substance which emits a fluorescence in solidstate and having a number-average molecular weight of 1×10⁴ to 1×10⁸ interms of polystyrene, wherein the substance contains at least onerepeating unit represented by the above-described formula (1). Morepreferably the substance contains each one or more of repeating unitsrepresented by the above-described formula (2), formula (3) or formula(4), respectively.

[0026] In the above formula (1), Ar₁ is a divalent group formingcarbon—carbon bonds with adjacent two groups respectively, the divalentgroup being an arylene group having 6 to 60 carbon atoms participatingin conjugation or a heterocyclic compound group having 3 to 60 carbonatoms participating in conjugation, and the arylene group andheterocyclic compound group may further have a substituent. Each of R₁and R₂ independently represents a group selected from the groupconsisting of a hydrogen atom, linear, branched or cyclic alkyl groupshaving 1 to 20 carbon atoms, aryl groups having 6 to 60 carbon atoms,heterocyclic compound groups having 3 to 60 carbon atoms and a cyanogroup, and the aryl group and heterocyclic compound group may furtherhave a substituent. The symbol j is 0 or 1.

[0027] In the above formula (2), Ar₂ is an arylene group having 6 to 60carbon atoms contained in the main chain portion or a divalentheterocyclic compound group having 3 to 60 carbon atoms contained in themain chain portion. R₃ represents a group selected from the groupconsisting of linear, branched or cyclic alkyl groups having 1 to 20carbon atoms, mono, di or trialkylsilyl groups having 1 to 60 carbonatoms, aryl groups having 6 to 60 carbon atoms, arylalkyl groups having7 to 60 carbon atoms and heterocyclic compound groups having 3 to 60carbon atoms, and the aryl group, arylalkyl group and heterocyclic groupmay also have a substituent. X represents a group selected from —O—,—S—, —CR₁₁R₁₂—, —SiR₁₃R₁₄—, —NR₁₅—, —CO—, —COO—, —SO₂—, —CR₁₆═CR₁₇—, and—C≡C—. The symbol k is an integer from 1 to 4. R₄, R₅, and R₁₁—R₁₇represent, each independently, a group selected from the groupconsisting of a hydrogen atom, linear, branched or cyclic alkyl groupshaving 1 to 20 carbon atoms, aryl groups having 6 to 60 carbon atoms,heterocyclic compound groups having 3 to 60 carbon atoms and a cyanogroup, and the aryl group and heterocyclic group may also have asubstituent. The symbol m is 0 or 1.

[0028] Here, Ar₂ may have a substituent selected from the groupconsisting of linear, branched or cyclic alkyl groups having 1 to 20carbon atoms, mono, di or trialkylsilyl groups having 1 to 60 carbonatoms, mono or dialkylamino groups having 1 to 40 carbon atoms, arylgroups having 6 to 60 carbon atoms, arylalkyl groups having 7 to 60carbon atoms, arylamino groups having 6 to 60 carbon atoms, heterocycliccompound groups having 3 to 60 carbon atoms and a cyano group, and thearyl group, arylalkyl group, arylamino group and heterocyclic group mayfurther have a substituent. When Ar₂ has a plurality of substituents,they may be the same or different. One or more carbon atoms of thesubstituent on Ar₂ may be substituted with an oxygen atom or sulfuratom, and one or more hydrogen atoms of the substituent on Ar₂ may besubstituted with a fluorine atom.

[0029] In the above formula (3), Ar₃ is an arylene group having 6 to 60carbon atoms contained in the main chain portion or a heterocycliccompound group having 3 to 60 carbon atoms contained in the main chainportion. Ar₄ is an aryl group having 6 to 60 carbon atoms or aheterocyclic compound group having 3 to 60 carbon atoms, and may alsohave a substituent selected from the group consisting of linear,branched or cyclic alkyl groups having 1 to 20 carbon atoms, alkoxygroups having a linear, branched or cyclic alkyl group having 1 to 20carbon atoms, alkylthio groups having a linear, branched or cyclic alkylgroup having 1 to 20 carbon atoms, mono, di or trialkylsilyl groupshaving 1 to 60 carbon atoms, mono or dialkylamino groups having 1 to 40carbon atoms, aryl groups having 6 to 60 carbon atoms, aryloxy groupshaving 6 to 60 carbon atoms, arylalkyl groups having 7 to 60 carbonatoms, arylalkoxy groups having 7 to 60 carbon atoms, arylalkenyl groupshaving 8 to 60 carbon atoms, arylalkynyl groups having 8 to 60 carbonatoms, arylamino groups having 6 to 60 carbon atoms, heterocycliccompound groups having 3 to 60 carbon atoms and a cyano group, and thearyl group, aryloxy group, arylalkyl group, arylalkoxy group,arylalkenyl group, arylalkynyl group, arylamino group and heterocyclicgroup may further have a substituent. The symbol n is an integer from 1to 4. Each of R₆ and R₇ independently represents a group selected fromthe group consisting of a hydrogen atom, linear, branched or cyclicalkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 60carbon atoms, heterocyclic compound groups having 3 to 60 carbon atomsand a cyano group, and the aryl group and heterocyclic group may alsohave a substituent. The symbol p is 0 or 1. Ar₃ may have a substituentselected from the group consisting of linear, branched or cyclic alkylgroups having 1 to 20 carbon atoms, alkoxy groups having a linear;branched or cyclic alkyl group having 1 to 20 carbon atoms, alkylthiogroups having a linear, branched or cyclic alkyl group having 1 to 20carbon atoms, mono, di or trialkylsilyl groups having 1 to 60 carbonatoms, mono or dialkylamino groups having 1 to 40 carbon atoms, aryloxygroups having 6 to 60 carbon atoms, arylalkyl groups having 7 to 60carbon atoms, arylalkoxy groups having 7 to 60 carbon atoms, arylaminogroups having 6 to 60 carbon atoms, and a cyano group, and the aryloxygroup, arylalkyl group, arylalkoxy group, arylamino group may furtherhave a substituent. When Ar₃ has a plurality of substituents, they maybe the same or different. One or more carbon atoms of the substituentson Ar₃ may be substituted with an oxygen atom or sulfur atom, and one ormore hydrogen atoms of the substituents on Ar₃ may be substituted with afluorine atom.

[0030] In the above formula (4), Ar₅ is an arylene group having 6 to 60carbon atoms contained in the main chain portion or a divalentheterocyclic compound group having 3 to 60 carbon atoms contained in themain chain portion. R₈ represents a group selected from the groupconsisting of linear, branched or cyclic alkyl groups having 1 to 20carbon atoms, mono, di or trialkylsilyl groups having 1 to 60 carbonatoms, mono or dialkylamino groups having 1 to 40 carbon atoms,saturated heterocyclic compound groups having 3 to 60 carbon atoms andarylalkyl groups having 7 to 60 carbon atoms, and the arylalkyl groupmay further have a substituent. The symbol q is an integer from 1 to 4.Each of R₉ and R₁₀ independently represents a group selected from thegroup consisting of a hydrogen atom, linear, branched or cyclic alkylgroups having 1 to 20 carbon atoms, aryl groups having 6 to 60 carbonatoms, heterocyclic compound groups having 3 to 60 carbon atoms and acyano group, and the aryl group and heterocyclic group may also have asubstituent. The symbol r is 0 or 1. Ar₅ may have a substituent selectedfrom the group consisting of alkoxy groups having a linear, branched orcyclic alkyl group having 1 to 20 carbon atoms, alkylthio groups havinga linear, branched or cyclic alkyl group having 1 to 20 carbon atoms,aryl groups having 6 to 60 carbon atoms, aryloxy groups having 6 to 60carbon atoms, arylalkoxy groups having 7 to 60 carbon atoms, arylaminogroups having 6 to 60 carbon atoms, heterocyclic compound groups having3 to 60 carbon atoms and a cyano group, and the aryl group, aryloxygroup, arylalkoxy group, arylamino group and heterocyclic group mayfurther have a substituent. When Ar₅ has a plurality of substituents,they may be the same or different. One or more carbon atoms of thesubstituents on Ar₅ may be substituted with an oxygen atom or sulfuratom, and one or more hydrogen atoms of the substituents on Ar₅ may besubstituted with a fluorine atom.

[0031] In the polymer fluorescent substance of the present invention,containing each of the repeating units represented by repeating units ofthe formulae (2), (3) and (4) respectively, the total amount ofrepeating units of the formulae (2), (3) and (4) is, preferably, 50 mol% or more based on all repeating units, and the amount of repeatingunits of the formula (2) is 0.1 mol % to 30 mol %, the amount ofrepeating units of the formula (3) is 29.9 mol % to 70 mol % and theamount of repeating units of the formula (4) is 29.9 mol % to 70 mol %,based on the total amount of repeating units of the formulae (2), (3)and (4).

[0032] The amount of repeating units of the formula (2) is, morepreferably, 0.2 mol % to 20 mol %, and further preferably, 1 mol % to 10mol %, based on the total amount of repeating units of the formulae (2),(3) and (4).

[0033] In the formula (2), Ar₂, preferably, is an arylene group having 6to 20 carbon atoms contained in the main chain and X is an oxygen atom,in the formula (3), Ar₃ is an arylene group having 6 to 20 carbon atomscontained in the main chain, and more preferably, in the formula (4),Ar₅ is an arylene group having 6 to 20 carbon atoms contained in themain chain.

[0034] In the formula (4), R₈ is, preferably, a mono, di ortrialkylsilyl group having 1 to 60 carbon atoms.

[0035] Further preferably, the polymer fluorescent substance comprisingat least four repeating units of the formulae (2), (3) and (4).

[0036] In the formulas (1) to (4), Ar₁, Ar₂, Ar₃, and Ar₅ are,respectively, an arylene group having 6 to 20 carbon atoms contained inthe main chain or a heterocyclic compound group having 2 to 20 carbonatoms contained in the main chain.

[0037] Ar₁, Ar₂, Ar₃, and Ar₅ can be selected so as not to deterioratethe fluorescence property of the polymer fluorescent substance, andexemplified are divalent groups below described chemical formulas 7 to20.

[0038] In the above examples of Ar₂, Ar₃ and Ar₅, R is selected: to have1 to 4 substituent groups represented by —X—R₃, in case of Ar₂; to have1 to 4 substituent groups represented by Ar₄, in case of Ar₃; to have 1to 4 substituent groups represented by R₈, in case of Ar₅.

[0039] R other than the groups represented by —X—R₃, —Ar₄ or —R₈includes a hydrogen atom, linear, branched, or cyclic alkyl groupshaving 1 to 20 carbon atoms; linear, branched, or cyclic alkoxy groupshaving 1 to 20 carbon atoms; linear, branched, or cyclic alkylthiogroups having 1 to 20 carbon atoms; mono-, di-, or tri-alkylsilyl groupshaving 1 to 60 carbon atoms; mono-, or di-alkylamino group having 1 to40 carbon atoms; aryl groups having 6 to 60 carbon atoms; aryloxy groupshaving 6 to 60 carbon atoms; arylalkyl groups having 7 to 60 carbonatoms; arylalkoxy groups having 7 to 60 carbon atoms; arylamino groupshaving 6 to 60 carbon atoms; heterocyclic compound groups having 3 to 60carbon atoms and cyano group. The aryl group, aryloxy group, arylalkylgroup, arylalkoxy group and arylamino group may have furthersubstituents.

[0040] Carbon atoms in the group represented by above R are possiblyreplaced by oxygen atom or sulfur atom, one or more hydrogen atoms in Rgroup may be replaced by fluorine atom.

[0041] In the above examples, a plurality of Rs are present in onestructural formula, they may be the same or different, and they areselected independently each other. When Ar₁, Ar₂, Ar₃ or Ar₅ has aplurality of substituents, they may be the same or different. Forenhancing the solubility into a solvent, it is preferable that at leastone substituent other than a hydrogen atom is carried, and it ispreferable that the symmetric property of the form of a repeating unitincluding a substituent is low.

[0042] X represents a group selected from —O—, —S—, —CR₁₁R₁₂—,—SiR₁₃R₁₄—, —NR₁₅—, —CO—, —COO—, —SO₂—, —CR₁₆═CR₁₇—, and —C≡C—. —O—,—S—, —CR₁₆═CR₁₇—, or —C≡C— is suitable, and —O— or —S— is more suitable,—O— is further more suitable. R₁₁ to R₁₇ represent, each independently,a hydrogen atom, linear, branched or cyclic alkyl group having 1-20carbon atoms, aryl group having 6-60 carbon atoms, heterocyclic compoundgroup having 3-60 carbon atoms, and a cyano group. The aryl group andthe heterocyclic compound group may have further substituents.

[0043] Concrete examples of R₃ and R₈ include: linear, branched andcyclic alkyl groups of 1 to 20 carbon atoms such as methyl group, ethylgroup, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group,tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group,nonyl group, decyl group, lauryl group, cyclopropyl group, cyclobutylgroup, cyclopentyl group, cyclohexyl group, cycloheptyl group,cyclooctyl group, cyclononyl group, cyclododecyl group, and the like,and pentyl group, hexyl group, octyl group, decyl group and cyclohexylgroup are preferable. As to the illustrated examples of alkyl groups,when prefixes, such as n- and iso-, are not specifically shown, theillustrated examples include all the alkyl groups of linear and branchedstructures. (Hereinafter referred to as the same).

[0044] Examples of mono-, di- and tri-alkylsilyl group of 1 to 60 carbonatoms include: mono-methylsilyl group, dimethylsilyl group,trimethylsilyl group, mono-ethylsilyl group, diethylsilyl group,triethylsilyl group, mono-propylsilyl group, dipropylsilyl group,tripropylsilyl group, mono-butylsilyl group, dibutylsilyl group,tributylsilyl group, mono-pentylsilyl group, dipentylsilyl group,tripentylsilyl group, mono-hexylsilyl group, dihexylsilyl group,trihexylsilyl group, mono-heptylsilyl group, diheptylsilyl group,triheptylsilyl group, mono-octylsilyl group, dioctylsilyl group,trioctylsilyl group, mono-nonylsilyl group, dinonylsilyl group,trinonylsilyl group, mono-decylsilyl group, didecylsilyl group,tridecylsilyl group, mono-laurylsilyl group, dilaurylsilyl group,trilaurylsilyl group, ethyldimethylsilyl group, propyldimethylsilylgroup, butyldimethylsilyl group, pentyldimethylsilyl group,hexyldimethylsilyl group, heptyldimethylsilyl group, octyldimethylsilylgroup, nonyldimethylsilyl group, decyldimethylsilyl group,lauryldimethylsilyl group and the like, and tripentylsilyl group,trihexylsilyl group, trioctylsilyl group, tridecylsilyl group,pentyldimethylsilyl group, hexyldimethylsilyl group, octyldimethylsilylgroup decyldimethylsilyl group and dodecyldimethylsilyl group arepreferable.

[0045] Examples of an arylalkyl group having 7-60 carbon atoms, includephenylmethyl group, phenylethyl group, phenylpropyl group, C₁-C₁₂alkoxyphenylmethyl group, C₁-C₁₂ alkoxyphenylethyl group, C₁-C₁₂alkoxyphenylpropyl group, C₁-C₁₂ alkylphenylmethyl group, C₁-C₁₂alkylphenylethyl group, C₁-C₁₂ alkylphenylpropyl group, naphtylmethylgroup, naphtylethyl group, naphtylpropyl group, and the like. Amongthem, C₁-C₁₂ alkoxyphenylmethyl group, C₁-C₁₂ alkoxyphenylethyl group,C₁-C₁₂ alkoxyphenylpropyl group, C₁-C₁₂ alkylphenylmethyl group, C₁-C₁₂alkylphenylethyl group, C₁-C₁₂ alkylphenylpropyl group are suitable.

[0046] As an aryl group having 6-60 carbon atoms, concrete examples ofR₃ and Ar₄ include phenyl group, C₁-C₁₂ alkoxyphenyl group (C₁-C₁₂represents that the number of carbon atoms are 1-12. Hereinafter,referred to as the same.), C₁-C₁₂ alkylphenyl group, 1-naphtyl group,2-naphtyl group, and the like. Among them, C₁-C₁₂ alkoxyphenyl group,and C₁-C₁₂ alkylphenyl group are suitable. Moreover, examples of aheterocyclic compound group having 4-60 carbon atoms include thienylgroup, C₁-C₁₂ alkylthienyl group, pyroryl group, furyl group, pyridylgroup, C₁-C₁₂ alkylpyridyl group, and the like. Among them, thienylgroup, C₁-C₁₂ alkylthienyl group, pyridyl group, and C₁-C₁₂ alkylpyridylgroup are suitable.

[0047] As a saturated heterocyclic compound group having 3-60 carbonatoms, concrete examples of R₈ include oxolanyl group, dioxolanyl group,thiolanyl group, oxathiolanyl grouop, pyrrolidinyl group, pyrrolidinogroup, pyrazolidyl group, imidazolidyl group, oxanyl group, thianylgroup, piperidyl group, piperidino group, piperazinyl group, piperazinogroup, morpholinyl group, morpholino group, and the like. Oxolanyl groupand oxanyl group are suitable.

[0048] Examples of mono- or di-alkylamino group having 1-40 carbon atomsinclude monomethylamino group, dimethylamino group, monoethylaminogroup, diethylamino group, monopropylamino group, dipropylamino group,monobutylamino group, dibutylamino group, monopentylamino group,dipentylamino group, monohexylamino group, dihexylamino group,monoheptylamino group, diheptylamino group, monooctylamino group,dioctylamino group, and the like. Pentylamino group, hexylamino group,octylamino group, decylamino group, dipentylamino group, dihexylaminogroup, dioctylamino group, and didecylamino group are suitable.

[0049] If the case where R are substituents other than hydrogen atom,cyano group, or a group represented by —X—R₃, —Ar₄, or —R₈, examples ofa linear, branched or cyclic alkyl group of having 1-20 carbon atomsinclude methyl group, ethyl group, n-propyl group, iso-propyl group,n-butyl group, iso-butyl group, tert-butyl group, pentyl group, hexylgroup, heptyl group, octyl group, nonyl group, decyl group, laurylgroup, cyclopropyl group, cyclobutyl group, cyclopentyl group,cyclohexyl group, cycloheptyl group, cyclooctyl group, cyclononyl group,cyclododecyl group, and the like. Pentyl group, hexyl group, octylgroup, decyl group, and cyclohexyl group are suitable.

[0050] Examples of an alkoxy group having a linear, branched or cyclicalkyl group having 1-20 carbon atoms, include methoxy group, ethoxygroup, n-propyloxy group, iso-propyloxy group, n-butoxy group,iso-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group,heptyloxy group, octyloxy group, nonyloxy group, decyloxy group,lauryloxy group, cyclopropyloxy group, cyclobutyloxy group,cyclopentyloxy group, cyclohexyloxy group, cycloheptyloxy group, and thelike. Pentyloxy group, hexyloxy group, octyloxy group, decyloxy group,and cyclohexyloxy group are suitable.

[0051] Examples of an alkylthio group having a linear, branched orcyclic alkyl group having 1-20 carbon atoms, include methylthio group,ethylthio group, n-propylthio group, iso-propylthio group, n-butylthiogroup, iso-butylthio group, tert-butylthio group, pentylthio group,hexylthio group, heptylthio group, octylthio group, nonylthio group,decylthio group, laurylthio group, cyclopropylthio group, cyclobutylthiogroup, cyclopentylthio group, cyclohexylthio group, cycloheptylthiogroup, and the like. Pentylthio group, hexylthio group, octylthio group,decylthio group, and cyclohexylthio group are suitable.

[0052] Examples of linear, branched or cyclic alkylsilyl group having1-60 carbon atoms include monomethylsilyl group, dimethylsilyl group,trimethylsilyl group, monoethylsilyl group, diethylsilyl group,triethylsilyl group, monopropylsilyl group, dipropylsilyl group,tripropylsilyl group, monobutylsilyl group, dibutylsilyl group,tributylsilyl group, monopentylsilyl group, dipentylsilyl group,tripentylsilyl group, monohexylsilyl group, dihexylsilyl group,trihexylsilyl group, monoheptylsilyl group, diheptylsilyl group,triheptylsilyl group, monooctylsilyl group, dioctylsilyl group,monooctylsilyl group, dioctylsilyl group, trioctylsilyl group,monononylsilyl group, dinonylsilyl group, trinonylsilyl group,monodecylsilyl group, didecylsilyl group, tridecylsilyl group,monolaurylsilyl group, dilaurylsilyl group, trilaurylsilyl group,ethyldimethylsilyl group, propyldimethylsilyl group, butyldimethylsilylgroup, pentyldimethylsilyl group, hexyldimethylsilyl group,heptyldimethylsilyl group, octyldimethylsilyl group, nonyldimethylsilylgroup, decyldimethylsilyl group, lauryldimethylsilyl group, and thelike.

[0053] Among them, tripentylsilyl group, trihexylsilyl group,trioctylsilyl group, tridecylsilyl group, pentyldimethylsilyl group,hexyldimethylsilyl group, octyldimethylsilyl group, anddecyldimethylsilyl group are suitable.

[0054] Examples of the mono- or di-alkylamino group having 1-40 carbonatoms include monomethylamino group, dimethylamino group, monoethylamino group, diethylamino group, monopropylamino group,dipropylamino group, monobutylamino group, dibutylamino group,monopentylamino group, dipentylamino group, monohexylamino group,dihexylamino group, monoheptylamino group, diheptylamino group,monooctylamino group, dioctylamino group, monononylamino group,dinonylamino group, monodecylamino group, didecylamino group,monolaurylamino group, dilaurylamino group, and the like. Among them,pentylamino group, hexylamino group, octylamino group, decylamino group,dipentylamino group, dihexylamino group, dioctylamino group, anddidecylamino group are suitable.

[0055] Examples of an aryl group having 6-60 carbon atoms include phenylgroup, C₁-C₁₂ alkoxyphenyl group (C₁-C₁₂ represents that the number ofcarbon atoms are 1-12. Hereinafter, referred to as the same.), C₁-C₁₂alkylphenyl group, 1-naphtyl group, 2-naphtyl group, and the like. Amongthem, C₁-C₁₂ alkoxyphenyl group, and C₁-C₁₂ alkylphenyl group aresuitable.

[0056] Examples of an aryloxy group having 6-60 carbon atoms includephenoxy group, C₁-C₁₂ alkoxyphenoxy group, C₁-C₁₂ alkylphenoxy group,1-naphtyloxy group, 2-naphtyloxy group, and the like. Among them, C₁-C₁₂alkoxyphenoxy group, and C₁-C₁₂ alkylphenoxy group are suitable.

[0057] Examples of an arylalkyl group having 7-60 carbon atoms includephenyl-C₁-C₁₂ alkyl group, C₁-C₁₂ alkoxyphenyl-C₁-C₁₂ alkyl group,C₁-C₁₂ alkylphenyl-C₁-C₁₂ alkyl group, 1-naphtyl-C₁-C₁₂ alkyl group,2-naphtyl-C₁-C₁₂ alkyl group, and the like. Among them, C₁-C₁₂alkoxyphenyl-C₁-C₁₂ alkyl group, and C₁-C₁₂ alkylphenyl-C₁-C₁₂ alkylgroup are suitable.

[0058] Examples of an arylalkoxy group having 7-60 carbon atoms includephenyl-C₁-C₁₂ alkoxy group, C₁-C₁₂ alkoxyphenyl-C₁-C₁₂ alkoxygroup,C₁-C₁₂ alkylphenyl-C₁-C₁₂ alkoxy group, 1-naphtyl-C₁-C₁₂ alkoxy group,2-naphtyl-C₁-C₁₂ alkoxy group, and the like.

[0059] Among them, C₁-C₁₂ alkoxyphenyl-C₁-C₁₂ alkoxy group, and C₁-C₁₂alkylphenyl-C₁-C₁₂ alkoxy group are suitable.

[0060] As an arylalkenyl group having 8-60 carbon atoms, phenylethenylgroup, naphtylethenyl group, anthrylethenyl group, pyrenylethenyl group,etc. are exemplified. These may have further C₁-C₁₂ alkyl group, C₁-C₁₂alkoxy group, and C₆-C₂₀ aryl group as a substituent. Among them,phenylethenyl group, phenylethenyl group having C₁-C₁₂ alkoxy group, thephenylethenyl group having C₁-C₁₂ alkyl group are suitable.

[0061] As an arylalkynyl group having 8-60 carbon atoms, phenylethynylgroup, naphtylethynyl group, anthrylethynyl group, pyrenylethynyl group,etc. are exemplified. These may have further C₁-C₁₂ alkyl group, C₁-C₁₂alkoxy group, and C₆-C₂₀ aryl group as a substituent. Phenyl ethynylgroup, phenylethynyl group having C₁-C₁₂ alkoxy group, and phenylethynylgroup having C₁-C₁₂ alkyl group are suitable.

[0062] Examples of a mono or diarylamino group having 6-60 carbon atomsinclude phenylamino group, diphenylamino group, C₁-C₁₂ alkoxyphenylaminogroup, a di-(C₁-C₁₂ alkoxyphenyl) amino group, a di-(C₁-C₁₂ alkylphenyl)amino group, 1-naphtylamino group, 2-naphtylamino group, and the likeAmong them, C₁-C₁₂ alkylphenylamino group, and a fW (C₁-C₁₂ alkylphenyl)amino group are suitable.

[0063] As a heterocyclic compound group having 3-60 carbon atoms,pyrrolyl group, oxazolyl group, isoxazolyl group, thiazolyl group,isothiazolyl group, pyranyl group, pyridyl group, pyridazinyl group,pyrimidyl group, pyrazyl group, quinolyl group, oxazyl group, dioxazylgroup, indolyl group, isoindolyl group, indazolyl group, chromenylgroup, quinolyl group, isoquinolyl group, cinnolyl group, quinazolylgroup, quinoxalyl group, phthalazyl group, purinyl group, pteridylgroup, xanthenyl group, carbazolyl group, phenanthridyl group, acridylgroup, phnazyl group, phennthrolyl group, thianaphtalenyl group,dithianaphtalenyl group, furyl group, benzofuryl group, dibenzofurylgroup, thienyl group, benzothienyl group, dibenzothienyl group,oxadiazolyl group, oxazolyl group, triazolylgroup, thiodiazolyl group,benzoxazolyl group, benzodiazolyl group, silolyl group,benzosilolylgroup, etc. are exemplified. These may have further C₁-C₁₂alkyl group, C₁-C₁₂ alkoxy group, and C₆-C₂₀ aryl group as asubstituent. A heterocyclic compound group having 4-60 carbon atoms ispreferable, and more preferably, a heterocyclic compound group having4-30 carbon atoms. Thienyl group, thienyl group having C₁-C₁₂ alkylgroup, pyridyl group, and pyridyl group having C₁-C₁₂ alkyl group issuitable.

[0064] Among the examples of R, the substituent containing an alkylchain can be either of linear, branched, or cyclic one, or thecombination thereof. When it is not linear, exemplified are isoamylgroup, 2-ethylhexyl group, 3,7-dimethyloctyl group, cyclohexyl group,4-C₁-C₁₂ alkylcyclohexyl group, and the like. In order to improve thesolubility to solvent of a polymeric fluorescent substance, it issuitable that a cyclic or branched alkyl chain is contained in one ofthe substituents of Ar₁, Ar₂, Ar₄, and Ar₅. Moreover, the terminal endsof two alkyl chains can be connected to form a ring. Furthermore, carbonatoms of a part of alkyl chain may be replaced by a group containning ahetero atom. Examples of hetero atoms include an oxygen atom, a sulfuratom, a nitrogen atom, and the like.

[0065] Furthermore, among the examples of R, when an aryl group or aheterocyclic compound group is contained in the part, they can containone or more substituents.

[0066] In the above formula (1), the symbol m is 0 or 1. In the aboveformula (2), the symbol p is 0 or 1. In the above formula (3), thesymbol r is 0 or 1. R₁, R₂ in the above formula (1), R₄, R₅ in the aboveformula (2), R₆, R₇ in the above formula (3), and R₉ and R₁₀ in theabove formula (3) represent each independently, a group selected from ahydrogen atom, a linear, branched and cyclic alkyl group having 1-20carbon atoms, an aryl group having 6-60 carbon atoms, a heterocycliccompound group having 4-60 carbon atoms and cyano group. The aryl groupand the heterocyclic compound group may have substituents.

[0067] When R₁, R₂, R₄-R₇, R₉ and R₁₀ are substituents other than ahydrogen atom or a cyano group, examples of a linear, branched or cyclicalkyl group having 1-20 carbon atoms include methyl group, ethyl group,n-propyl group, iso-propyl group, n-butyl group, iso-butyl group,tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group,nonyl group, decyl group, lauryl group, cyclopropyl group, cyclobutylgroup, cyclopentyl group, cyclohexyl group, cycloheptyl group,cyclooctyl group, cyclononyl group, cyclododecyl group, and the like.Among them, pentyl group, hexyl group, octyl group, decyl group, andcyclohexyl group are suitable.

[0068] Examples of an aryl group having 6-60 carbon atoms include phenylgroup, C₁-C₁₂ alkoxyphenyl group, C₁-C₁₂ alkylphenyl group, 1-naphtylgroup, 2-naphtyl group, and the like. Among them, phenyl group, andC₁-C₁₂ alkylphenyl group are suitable.

[0069] As a heterocyclic compound group having 3-60 carbon atoms,pyrrolyl group, oxazolyl group, isoxazolyl group, thiazolyl group,isothiazolyl group, pyranyl group, pyridyl group, pyridazinyl group,pyrimidyl group, pyrazyl group, quinolyl group, oxazyl group, dioxazylgroup, indolyl group, isoindolyl group, indazolyl group, chromenylgroup, quinolyl group, isoquinolyl group, cinnolyl group, quinazolylgroup, quiozalyl group, phthalazyl group, purinyl group, pteridyl group,xanthenyl group, carbazolyl group, phenanthridyl group, acridyl group,phnazyl group, phennthrolyl group, thianaphtalenyl group,dithianaphtalenyl group, furyl group, benzofuryl group, dibenzofurylgroup, thienyl group, benzothienyl group, dibenzothienyl group,oxadiazolyl group, oxazolyl group, triazolylgroup, thiodiazolyl group,benzoxazolyl group, benzodiazolyl group, silolyl group,benzosilolylgroup, etc. are exemplified. These may have further C₁-C₁₂alkyl group, C₁-C₁₂ alkoxy group, and C₆-C₂₀ aryl group as asubstituent. A heterocyclic compound group having 4-60 carbon atoms ispreferable, and more preferably, a heterocyclic compound group having4-30 carbon atoms. Thienyl group, thienyl group having C₁-C₁₂ alkylgroup, pyridyl group, and pyridyl group having C₁-C₁₂ alkyl group issuitable.

[0070] Moreover, as for the end group of a polymeric fluorescentsubstance, if the polymerizable group remains as it is, thelight-emitting property and lifetime of a device using thereof may fall,and it can be protected by a stable group.

[0071] Preferable is a conjugated bond successively connected to theconjugated structure of a main chain. For example, structures bonding toan aryl group or a heterocyclic compound group through vinylene groupare included. Specifically, a substituent such as the chemical formula10 described in JP-A 9-45478 is exemplified.

[0072] For synthesizing this polymeric fluorescent substance, when themain chain has vinylene groups, there are exemplified methods describedin JP-A No. 5-202355. Namely, there are exemplified polymerization ofdialdehyde compounds with diphosphonium salt compounds, polymerizationof dialdehyde compounds with bisphosphate ester compounds by Wittigreaction such as Horner-Wadsworth-Emmons method, condensationpolymerization by dehydrogenation method of a compound having two methylhalide groups, condensation polymerization by sulfonium saltdecomposition method of a compound having two sulfonium base group,polymerization of dialdehyde compounds with diacetonitrile compounds orof compounds having both of aldehyde and acetonitrile groups by theKnoevenagel reaction, and the like. Among them, polymerization by Wittigreaction, condensation polymerization by dehydrohalogenation method andcondensation polymerization by sulfonium salt decomposition method areeasy to conduct, as described in JP-A-3-244630.

[0073] Further, when the main chain does not have a vinylene group,there are exemplified a method in which polymerization is conducted fromthe corresponding monomer by the Suzuki coupling reaction, a method inwhich polymerization is conducted by the Grignard reaction, a method inwhich polymerization is conducted using a Ni(0) catalyst, a method inwhich polymerization is conducted using an oxidizing agents such asFeCl₃ and the like, a method in which oxidation polymerization isconducted electrochemically, a method in which an intermediate polymerhaving a suitable releasing group is decomposed, and the like.

[0074] This polymeric fluorescent substance may contain other repeatingunit than the repeating unit of the formulae (1), (2), (3) or (4) in therange wherein luminescent property and charge transport property do notdeteriorate. The repeating unit of the formulae (1), (2), (3), (4) orother unit than the repeating unit of the formulae (1), (2), (3) or (4)may be connected via a non-conjugated unit, or such non-conjugated partmay also contained in the repeating unit. As the linkage structure,there are exemplified those shown in the following chemical formula 21,combinations of those shown in the following chemical formula 21 with avinylene group, combinations of two or more of those shown in thefollowing chemical formula 21, and the like. Herein, R's eachindependently represents a group selected from the group exemplifiedabove, and Ar represents a hydrocarbon group of 6 to 60 carbon atoms.Specific examples of these groups are the same as those exemplifiedabove.

[0075] This polymeric fluorescent substance may also be a random, blockor graft copolymer, or a polymer having an intermediate structurethereof, for example, a random copolymer having blocking property. Fromthe viewpoint for obtaining a polymeric fluorescent substance havinghigh fluorescent quantum yield, random copolymers having blockingproperty and block or graft copolymers are more preferable than completerandom copolymers. Dendrimers or copolymers having branching in the mainchain and having three or more terminals are also included.

[0076] Further, as the polymeric fluorescent substance, those emittingfluorescence in a solid state are suitably used, since the materialutilizes light emission from a thin film.

[0077] As good solvents for the polymeric fluorescent substance, thereare exemplified chloroform, methylene chloride, dichloroethane,tetrahydrofuran, toluene, xylene, mesitylene, tetralin, decalin,n-butylbenzene and the like. The polymeric fluorescent substance can beusually dissolved in these solvents in an amount of 0.1 wt % or more,though the amount differs depending on the structure and molecularweight of the polymeric fluorescent substance.

[0078] The polymeric fluorescent substance has a number-averagemolecular weight of 1×10⁴ to 1×10⁸ in terms of polystyrene, and thedegree of polymerization thereof also changes depending on repeatingstructures and proportion thereof. From the standpoint of film formingproperty, generally the total amount of repeating structures ispreferably from 20 to 10000, more preferably from 30 to 10000,particularly preferably from 50 to 5000.

[0079] When these polymeric fluorescent substances are used as alight-emitting material of a polymer LED, the purity thereof exerts aninfluence on light-emitting property, therefore, it is preferable that amonomer before polymerization is purified by a method such asdistillation, sublimation purification, re-crystallization and the likebefore being polymerized and further, it is preferable to conduct apurification treatment such as re-precipitation purification,chromatographic separation and the like after the synthesis.

[0080] Moreover, the ratio of hole drift mobility μ_(H) to electrondrift mobility μ_(E) (μ_(H)/μ_(E)) of a polymeric fluorescent substanceused for polymer light-emitting diode of the present invention measuredby the Standard Time-of-Flight method is in the ranges of 0.1-10, andsuitably 0.2-5.

[0081] Especially, the hole drift mobility μ₀ without energetic disorderand spatial disorder in polymeric fluorescent substance, is suitablyless than 5×10⁻⁴ cm²/v/s, and more suitably less than 2×10⁻⁴ cm²/v/s.“The hole drift mobility 10 without energetic disorder and spatialdisorder” is defined by the following formula (1) according to Phys.Stat. Sol. (b) Vol.107 (1981) p.9.

[0082] The value of μ₀ is obtained by the Standard Time-of-Flightmethod, with measuring hole drift mobility μ (E, T) of a polymericfluorescent substance with changing electric field (E) and/ortemperature (T) and applying to the following formula (1).$\begin{matrix}{{\mu ( {E,T} )} = {\mu_{0}{\exp \lbrack {- ( \frac{2\quad \sigma}{3{kT}} )^{2}} \rbrack}\exp \{ {E^{1/2}{C\lbrack {( \frac{\quad \sigma}{k\quad T} )^{2} - \sum^{2}} \rbrack}} \}}} & (1)\end{matrix}$

[0083] E is electric field, T is absolute temperature, μ (E, T) is holedrift mobility at electric field E and temperature T, k is Boltzmann'sconstant, C is a constant. σ is the degree of energetic disorderrepresenting the Gaussian width of energetic distribution of a hoppingsite, Σ is the degree of spatial disorder representing the Gaussianwidth of spatial distribution of a hopping site.

[0084] Specifically, applying to the formula (1) is carried out asfollows. Namely, E^(1/2) and log[μ (E, T)] are plotted at eachtemperature T, by using the measured hole drift mobility μ (E, T) andelectric field E. Straight line approximation by a least-square methodis carried out, and the intercept value μ (E→0, T) of the straight lineis obtained.

[0085] Subsequently, 1/T² and log[μ (E→0, T)] are plotted, straight lineapproximation by a least-square method is carried out, and the value μ₀is obtained from the intercept of the straight line.

[0086] In the above, the temperature of hole drift mobility μ (E, T)measurement are usually changed in a range of from liquid nitrogentemperature to 80° C., and the electric field is usually changed in therange of 10-10⁷ v/cm.

[0087] The Standard Time-of-Flight method used for measurement of theabove drift mobility is described in F. K. Dolezalek, Photoconductivityand Related Phenomena, Eds. J. Mort & D. M. Pai(New York) Chap.2(1976)p.27).

[0088] Next, the polymer LED of the present invention will beillustrated. The polymer LED of the present invention is a polymer LEDcomprising a pair of electrodes composed of an anode and a cathode atleast one of which is transparent or semitransparent and alight-emitting layer disposed between the electrodes, and a polymericfluorescent substance of the present invention is contained in thelight-emitting layer.

[0089] As the polymer LED of the present invention, there are listedpolymer LEDs having an electron-transporting layer disposed between acathode and a light-emitting layer, polymer LEDs having ahole-transporting layer disposed between an anode and a light-emittinglayer, polymer LEDs having an electron-transporting layer disposedbetween a cathode and a light-emitting layer and having ahole-transporting layer disposed between an anode and a light-emittinglayer.

[0090] For example, the following structures a) to d) are specificallyexemplified.

[0091] a) anode/light-emitting layer/cathode

[0092] b) anode/hole-transporting layer/light-emitting layer/cathode

[0093] c) anode/light-emitting layer/electron-transportinglayer//cathode

[0094] d) anode/hole-transporting layer/light-emittinglayer/electron-transporting layer/cathode (wherein, / indicates adjacentlamination of layers. Hereinafter, referred to as the same)

[0095] Herein, the light-emitting layer is a layer having function toemit a light, the hole-transporting layer is a layer having function totransport a hole, and the electron-transporting layer is a layer havingfunction to transport an electron. Herein, the electron-transportinglayer and the hole-transporting layer are generically called acharge-transporting layer.

[0096] The light-emitting layer, hole-transporting layer andelectron-transporting layer may also each independently used in two ormore layers.

[0097] Of charge-transporting layers disposed adjacent to an electrode,that having function to improve charge-injecting efficiency from theelectrode and having effect to decrease driving voltage of an device areparticularly called sometimes a charge-injecting layer (hole-injectinglayer, electron-injecting layer) in general.

[0098] For enhancing adherence with an electrode and improving chargeinjection from an electrode, the above-described charge-injecting layeror insulation layer having a thickness of 2 nm or less may also beprovided adjacent to an electrode, and further, for enhancing adherenceof the interface, preventing mixing and the like, a thin buffer layermay also be inserted into the interface of a charge-transporting layerand light-emitting layer.

[0099] The order and number of layers laminated and the thickness ofeach layer can be appropriately applied while considering light-emittingefficiency and life of the device.

[0100] In the present invention, as the polymer LED having acharge-injecting layer (electron-injecting layer, hole-injecting layer)provided, there are listed a polymer LED having a charge-injecting layerprovided adjacent to a cathode and a polymer LED having acharge-injecting layer provided adjacent to an anode.

[0101] For example, the following structures e) to p) are specificallyexemplified.

[0102] e) anode/charge-injecting layer/light-emitting layer/cathode

[0103] f) anode/light-emitting layer/charge injecting layer/cathode

[0104] g) anode/charge-injecting layer/light-emittinglayer/charge-injecting layer/cathode

[0105] h) anode/charge-injecting layer/hole-transportinglayer/light-emitting layer/cathode

[0106] i) anode/hole-transporting layer/light-emittinglayer/charge-injecting layer/cathode

[0107] j) anode/charge-injecting layer/hole-transportinglayer/light-emitting layer/charge-injecting layer/cathode

[0108] k) anode/charge-injecting layer/light-emittinglayer/electron-transporting layer/cathode

[0109] l) anode/light-emitting layer/electron-transportinglayer/charge-injecting layer/cathode

[0110] m) anode/charge-injecting layer/light-emittinglayer/electron-transporting layer/charge-injecting layer/cathode

[0111] n) anode/charge-injecting layer/hole-transportinglayer/light-emitting layer/electron-transporting layer/cathode

[0112] o) anode/hole-transporting layer/light-emittinglayer/electron-transporting layer/charge-injecting layer/cathode

[0113] p) anode/charge-injecting layer/hole-transportinglayer/light-emitting layer/electron-transporting layer/charge-injectinglayer/cathode

[0114] As the specific examples of the charge-injecting layer, there areexemplified layers containing an conducting polymer, layers which aredisposed between an anode and a hole-transporting layer and contain amaterial having an ionization potential between the ionization potentialof an anode material and the ionization potential of a hole-transportingmaterial contained in the hole-transporting layer, layers which aredisposed between a cathode and an electron-transporting layer andcontain a material having an electron affinity between the electronaffinity of a cathode material and the electron affinity of anelectron-transporting material contained in the electron-transportinglayer, and the like.

[0115] When the above-described charge-injecting layer is a layercontaining an conducting polymer, the electric conductivity of theconducting polymer is preferably 10⁻⁵ S/cm or more and 10³ S/cm or less,and for decreasing the leak current between light-emitting pixels, morepreferably 10⁻⁵S/cm or more and 10² S/cm or less, further preferably10⁻⁵ S/cm or more and 10¹ S/cm or less.

[0116] Usually, to provide an electric conductivity of the conductingpolymer of 10⁻⁵ S/cm or more and 10³ S/cm or less, a suitable amount ofions are doped into the conducting polymer.

[0117] Regarding the kind of an ion doped, an anion is used in ahole-injecting layer and a cation is used in an electron-injectinglayer. As examples of the anion, a polystyrene sulfonate ion,alkylbenzene sulfonate ion, camphor sulfonate ion and the like areexemplified, and as examples of the cation, a lithium ion, sodium ion,potassium ion, tetrabutyl ammonium ion and the like are exemplified.

[0118] The thickness of the charge-injecting layer is for example, from1 nm to 100 nm, preferably from 2 nm to 50 nm.

[0119] Materials used in the charge-injecting layer may properly beselected in view of relation with the materials of electrode andadjacent layers, and there are exemplified conducting polymers such aspolyaniline and derivatives thereof, polythiophene and derivativesthereof, polypyrrole and derivatives thereof, poly(phenylene vinylene)and derivatives thereof, poly(thienylene vinylene) and derivativesthereof, polyquinoline and derivatives thereof, polyquinoxaline andderivatives thereof, polymers containing aromatic amine structures inthe main chain or the side chain, and the like, and metal phthalocyanine(copper phthalocyanine and the like), carbon and the like.

[0120] The insulation layer having a thickness of 2 nm or less hasfunction to make charge injection easy. As the material of theabove-described insulation layer, metal fluoride, metal oxide, organicinsulation materials and the like are listed. As the polymer LED havingan insulation layer having a thickness of 2 nm or less, there are listedpolymer LEDs having an insulation layer having a thickness of 2 nm orless provided adjacent to a cathode, and polymer LEDs having aninsulation layer having a thickness of 2 nm or less provided adjacent toan anode.

[0121] Specifically, there are listed the following structures q) to ab)for example.

[0122] q) anode/insulation layer having a thickness of 2 nm orless/light-emitting layer/cathode

[0123] r) anode/light-emitting layer/insulation layer having a thicknessof 2 nm or less/cathode

[0124] s) anode/insulation layer having a thickness of 2 nm orless/light-emitting layer/insulation layer having a thickness of 2 nm orless/cathode

[0125] t) anode/insulation layer having a thickness of 2 nm orless/hole-transporting layer/light-emitting layer/cathode

[0126] u) anode/hole-transporting layer/light-emitting layer/insulationlayer having a thickness of 2 nm or less/cathode

[0127] v) anode/insulation layer having a thickness of 2 nm orless/hole-transporting layer/light-emitting layer/insulation layerhaving a thickness of 2 nm or less/cathode

[0128] w) anode/insulation layer having a thickness of 2 nm orless/light-emitting layer/electron-transporting layer/cathode

[0129] x) anode/light-emitting layer/electron-transportinglayer/insulation layer having a thickness of 2 nm or less/cathode

[0130] y) anode/insulation layer having a thickness of 2 nm orless/light-emitting layer/electron-transporting layer/insulation layerhaving a thickness of 2 nm or less/cathode

[0131] z) anode/insulation layer having a thickness of 2 nm orless/hole-transporting layer/light-emitting layer/electron-transportinglayer/cathode

[0132] aa) anode/hole-transporting layer/light-emittinglayer/electron-transporting layer/insulation layer having a thickness of2 nm or less/cathode

[0133] ab) anode/insulation layer having a thickness of 2 nm orless/hole-transporting layer/light-emitting layer/electron-transportinglayer/insulation layer having a thickness of 2 nm or less/cathode

[0134] In producing a polymer LED, when a film is formed from a solutionby using such polymeric fluorescent substance soluble in an organicsolvent, only required is removal of the solvent by drying after coatingof this solution, and even in the case of mixing of acharge-transporting material and a light-emitting material, the samemethod can be applied, causing an extreme advantage in production. Asthe film forming method from a solution, there can be used coatingmethods such as a spin coating method, casting method, micro gravurecoating method, gravure coating method, bar coating method, roll coatingmethod, wire bar coating method, dip coating method, spray coatingmethod, screen printing method, flexo printing method, offset printingmethod, inkjet printing method and the like.

[0135] Regarding the thickness of the light-emitting layer, the optimumvalue differs depending on material used, and may properly be selectedso that the driving voltage and the light-emitting efficiency becomeoptimum values, and for example, it is from 1 nm to 1 μm, preferablyfrom 2 nm to 500 nm, further preferably from 5 nm to 200 nm.

[0136] In the polymer LED of the present invention, light-emittingmaterials other than the above-described polymeric fluorescent substancecan also be mixed in a light-emitting layer. Further, in the polymer LEDof the present invention, the light-emitting layer containinglight-emitting materials other than the above-described polymericfluorescent substance may also be laminated with a light-emitting layercontaining the above-described polymeric fluorescent substance.

[0137] As the light-emitting material, known materials can be used. In acompound having lower molecular weight, there can be used, for example,naphthalene derivatives, anthracene or derivatives thereof, perylene orderivatives thereof; dyes such as polymethine dyes, xanthene dyes,coumarine dyes, cyanine dyes; metal complexes of 8-hydroxyquinoline orderivatives thereof, aromatic amine, tetraphenylcyclopentane orderivatives thereof, or tetraphenylbutadiene or derivatives thereof, andthe like.

[0138] Specifically, there can be used known compounds such as thosedescribed in JP-A Nos. 57-51781, 59-195393 and the like, for example.

[0139] When the polymer LED of the present invention has ahole-transporting layer, as the hole-transporting materials used, thereare exemplified polyvinylcarbazole or derivatives thereof, polysilane orderivatives thereof, polysiloxane derivatives having an aromatic aminein the side chain or the main chain, pyrazoline derivatives, arylaminederivatives, stilbene derivatives, triphenyldiamine derivatives,polyaniline or derivatives thereof, polythiophene or derivativesthereof, polypyrrole or derivatives thereof, poly(p-phenylenevinylene)or derivatives thereof, poly(2,5-thienylenevinylene) or derivativesthereof, or the like.

[0140] Specific examples of the hole-transporting material include thosedescribed in JP-A Nos. 63-70257, 63-175860, 2-135359, 2-135361,2-209988, 3-37992 and 3-152184.

[0141] Among them, as the hole-transporting materials used in thehole-transporting layer, preferable are polymer hole-transportingmaterials such as polyvinylcarbazole or derivatives thereof, polysilaneor derivatives thereof, polysiloxane derivatives having an aromaticamine compound group in the side chain or the main chain, polyaniline orderivatives thereof, polythiophene or derivatives thereof,poly(p-phenylenevinylene) or derivatives thereof,poly(2,5-thienylenevinylene) or derivatives thereof, or the like, andfurther preferable are polyvinylcarbazole or derivatives thereof,polysilane or derivatives thereof and polysiloxane derivatives having anaromatic amine compound group in the side chain or the main chain. Inthe case of a hole-transporting material having lower molecular weight,it is preferably dispersed in a polymer binder for use.

[0142] Polyvinylcarbazole or derivatives thereof are obtained, forexample, by cation polymerization or radical polymerization from a vinylmonomer.

[0143] As the polysilane or derivatives thereof, there are exemplifiedcompounds described in Chem. Rev., 89, 1359 (1989) and GB 2300196published specification, and the like. For synthesis, methods describedin them can be used, and a Kipping method can be suitably usedparticularly.

[0144] As the polysiloxane or derivatives thereof, those having thestructure of the above-described hole-transporting material having lowermolecular weight in the side chain or main chain, since the siloxaneskeleton structure has poor hole-transporting property. Particularly,there are exemplified those having an aromatic amine havinghole-transporting property in the side chain or main chain.

[0145] The method for forming a hole-transporting layer is notrestricted, and in the case of a hole-transporting layer having lowermolecular weight, a method in which the layer is formed from a mixedsolution with a polymer binder is exemplified. In the case of a polymerhole-transporting material, a method in which the layer is formed from asolution is exemplified.

[0146] The solvent used for the film forming from a solution is notparticularly restricted providing it can dissolve a hole-transportingmaterial. As the solvent, there are exemplified chlorine solvents suchas chloroform, methylene chloride, dichloroethane and the like, ethersolvents such as tetrahydrofuran and the like, aromatic hydrocarbonsolvents such as toluene, xylene and the like, ketone solvents such asacetone, methyl ethyl ketone and the like, and ester solvents such asethyl acetate, butyl acetate, ethylcellosolve acetate and the like.

[0147] As the film forming method from a solution, there can be usedcoating methods such as a spin coating method, casting method, microgravure coating method, gravure coating method, bar coating method, rollcoating method, wire bar coating method, dip coating method, spraycoating method, screen printing method, flexo printing method, offsetprinting method, inkjet printing method and the like, from a solution.

[0148] The polymer binder mixed is preferably that does not disturbcharge transport extremely, and that does not have strong absorption ofa visible light is suitably used. As such polymer binder, polycarbonate,polyacrylate, poly(methyl acrylate), poly(methyl methacrylate),polystyrene, poly (vinyl chloride), polysiloxane and the like areexemplified.

[0149] Regarding the thickness of the hole-transporting layer, theoptimum value differs depending on material used, and may properly beselected so that the driving voltage and the light-emitting efficiencybecome optimum values, and at least a thickness at which no pin hole isproduced is necessary, and too large thickness is not preferable sincethe driving voltage of the device increases. Therefore, the thickness ofthe hole-transporting layer is, for example, from 1 nm to 1 μm,preferably from 2 nm to 500 nm, further preferably from 5 nm to 200 nm.

[0150] When the polymer LED of the present invention has anelectron-transporting layer, known compounds are used as theelectron-transporting materials, and there are exemplified oxadiazolederivatives, anthraquinonedimethane or derivatives thereof, benzoquinoneor derivatives thereof, naphthoquinone or derivatives thereof,anthraquinone or derivatives thereof, tetracyanoanthraquinodimethane orderivatives thereof, fluorenone derivatives, diphenyldicyanoethylene orderivatives thereof, diphenoquinone derivatives, or metal complexes of8-hydroxyquinoline or derivatives thereof, polyquinoline and derivativesthereof, polyquinoxaline and derivatives thereof, polyfluorene orderivatives thereof, and the like.

[0151] Specifically, there are exemplified those described in JP-A Nos.63-70257, 63-175860, 2-135359, 2-135361, 2-209988, 3-37992 and 3-152184.

[0152] Among them, oxadiazole derivatives, benzoquinone or derivativesthereof, anthraquinone or derivatives thereof, or metal complexes of8-hydroxyquinoline or derivatives thereof, polyquinoline and derivativesthereof, polyquinoxaline and derivatives thereof, polyfluorene orderivatives thereof are preferable, and2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, benzoquinone,anthraquinone, tris(8-quinolinol)aluminum and polyquinoline are furtherpreferable.

[0153] The method for forming the electron-transporting layer is notparticularly restricted, and in the case of an electron-transportingmaterial having lower molecular weight, a vapor deposition method from apowder, or a method of film-forming from a solution or melted state isexemplified, and in the case of a polymer electron-transportingmaterial, a method of film-forming from a solution or melted state isexemplified, respectively.

[0154] The solvent used in the film-forming from a solution is notparticularly restricted provided it can dissolve electron-transportingmaterials and/or polymer binders. As the solvent, there are exemplifiedchlorine solvents such as chloroform, methylene chloride, dichloroethaneand the like, ether solvents such as tetrahydrofuran and the like,aromatic hydrocarbon solvents such as toluene, xylene and the like,ketone solvents such as acetone, methyl ethyl ketone and the like, andester solvents such as ethyl acetate, butyl acetate, ethylcellosolveacetate and the like.

[0155] As the film-forming method from a solution or melted state, therecan be used coating methods such as a spin coating method, castingmethod, micro gravure coating method, gravure coating method, barcoating method, roll coating method, wire bar coating method, dipcoating method, spray coating method, screen printing method, flexoprinting method, offset printing method, inkjet printing method and thelike.

[0156] The polymer binder to be mixed is preferably that which does notextremely disturb a charge transport property, and that does not havestrong absorption of a visible light is suitably used. As such polymerbinder, poly(N-vinylcarbazole), polyaniline or derivatives thereof,polythiophene or derivatives thereof, poly(p-phenylene vinylene) orderivatives thereof, poly(2,5-thienylene vinylene) or derivativesthereof, polycarbonate, polyacrylate, poly(methyl acrylate), poly(methylmethacrylate), polystyrene, poly(vinyl chloride), polysiloxane and thelike are exemplified.

[0157] Regarding the thickness of the electron-transporting layer, theoptimum value differs depending on material used, and may properly beselected so that the driving voltage and the light-emitting efficiencybecome optimum values, and at least a thickness at which no pin hole isproduced is necessary, and too large thickness is not preferable sincethe driving voltage of the device increases. Therefore, the thickness ofthe electron-transporting layer is, for example, from 1 nm to 1 μm,preferably from 2 nm to 500 nm, further preferably from 5 nm to 200 nm.

[0158] The substrate forming the polymer LED of the present inventionmay preferably be that does not change in forming an electrode andlayers of organic materials, and there are exemplified glass, plastics,polymer film, silicon substrates and the like. In the case of a opaquesubstrate, it is preferable that the opposite electrode is transparentor semitransparent.

[0159] In the present invention, it is preferable that an anode istransparent or semitransparent, and as the material of this anode,electron conductive metal oxide films, semitransparent metal thin filmsand the like are used. Specifically, there are used indium oxide, zincoxide, tin oxide, and films (NESA and the like) fabricated by using anelectron conductive glass composed of indium.tin.oxide (ITO),indium.zinc.oxide and the like, which are metal oxide complexes, andgold, platinum, silver, copper and the like are used, and among them,ITO, indium zinc oxide, tin oxide are preferable. As the fabricatingmethod, a vacuum vapor deposition method, sputtering method, ion platingmethod, plating method and the like are used. As the anode, there mayalso be used organic transparent conducting films such as polyaniline orderivatives thereof, polythiophene or derivatives thereof and the like.

[0160] The thickness of the anode can be appropriately selected whileconsidering transmission of a light and electric conductivity, and forexample, from 10 nm to 10 μm, preferably from 20 nm to 1 μm, furtherpreferably from 50 nm to 500 nm.

[0161] Further, for easy charge injection, there may be provided on theanode a layer comprising a phthalocyanine derivative conductingpolymers, carbon and the like, or a layer having an average filmthickness of 2 nm or less comprising a metal oxide, metal fluoride,organic insulating material and the like.

[0162] As the material of a cathode used in the polymer LED of thepresent invention, that having lower work function is preferable. Forexample, there are used metals such as lithium, sodium, potassium,rubidium, cesium, beryllium, magnesium, calcium, strontium, barium,aluminum, scandium, vanadium, zinc, yttrium, indium, cerium, samarium,europium, terbium, ytterbium and the like, or alloys comprising two ofmore of them, or alloys comprising one or more of them with one or moreof gold, silver, platinum, copper, manganese, titanium, cobalt, nickel,tungsten and tin, graphite or graphite intercalation compounds and thelike. Examples of alloys include a magnesium-silver alloy,magnesium-indium alloy, magnesium-aluminum alloy, indium-silver alloy,lithium-aluminum alloy, lithium-magnesium alloy, lithium-indium alloy,calcium-aluminum alloy and the like. The cathode may be formed into alaminated structure of two or more layers.

[0163] The thickness of the cathode can be appropriately selected whileconsidering transmission of a light and electric conductivity, and forexample, from 10 nm to 10 μm, preferably from 20 nm to 1 μm, furtherpreferably from 50 nm to 500 nm.

[0164] As the method for fabricating a cathode, there are used a vacuumvapor deposition method, sputtering method, lamination method in which ametal thin film is adhered under heat and pressure, and the like.Further, there may also be provided, between a cathode and an organiclayer, a layer comprising an conducting polymer, or a layer having anaverage film thickness of 2 nm or less comprising a metal oxide, metalfluoride, organic insulation material and the like, and afterfabrication of the cathode, a protective layer may also be providedwhich protects the polymer LED. For stable use of the polymer LED for along period of time, it is preferable to provide a protective layerand/or protective cover for protection of the device in order to preventit from outside damage.

[0165] As the protective layer, there can be used a polymer compound,metal oxide, metal fluoride, metal borate and the like. As theprotective cover, there can be used a glass plate, a plastic plate thesurface of which has been subjected to lower-water-permeation treatment,and the like, and there is suitably used a method in which the cover ispasted with an device substrate by a thermosetting resin or light-curingresin for sealing. If space is maintained using a spacer, it is easy toprevent an device from being injured. If an inner gas such as nitrogenand argon is sealed in this space, it is possible to prevent oxidationof a cathode, and further, by placing a desiccant such as barium oxideand the like in the above-described space, it is easy to suppress thedamage of an device by moisture adhered in the production process. Amongthem, any one means or more are preferably adopted.

[0166] For obtaining light emission in plane form using the polymer LEDof the present invention, an anode and a cathode in the plane form mayproperly be placed so that they are laminated each other. Further, forobtaining light emission in pattern form, there are a method in which amask with a window in pattern form is placed on the above-describedplane light-emitting device, a method in which an organic layer innon-light emission part is formed to obtain extremely large thicknessproviding substantial non-light emission, and a method in which any oneof an anode or a cathode, or both of them are formed in the pattern. Byforming a pattern by any of these methods and by placing some electrodesso that independent on/off is possible, there is obtained a displaydevice of segment type which can display digits, letters, simple marksand the like. Further, for forming a dot matrix device, it may beadvantageous that anodes and cathodes are made in the form of stripesand placed so that they cross at right angles. By a method in which aplurality of kinds of polymeric fluorescent substances emittingdifferent colors of lights are placed separately or a method in which acolor filter or luminescence converting filter is used, area colordisplays and multi color displays are obtained. A dot matrix display canbe driven by passive driving, or by active driving combined with TFT andthe like. These display devices can be used as a display of a computer,television, portable terminal, portable telephone, car navigation, viewfinder of a video camera, and the like.

[0167] Further, the above-described light-emitting device in plane formis a thin self-light-emitting one, and can be suitably used as a sheetlight source for back-light of a liquid crystal display, or as a sheetlight source for illumination. Further, if a flexible plate is used, itcan also be used as a curved light source or a display.

EXAMPLES

[0168] The following examples further illustrate the present inventionin detail but do not limit the scope thereof.

[0169] Herein, regarding the number average molecular weight, a numberaverage molecular weight in terms of polystyrene was measured by gelpermeation chromatography (GPC) using chloroform as a solvent.

Example 1

[0170] <Synthesis of Polymer Fluorescent Substance 1>

[0171] 0.244 g (7.3 mmol) of 2-methoxy-5-(2-ethylhexyloxy)-p-xylylenedichloride, 1.83 g (4.5 mmol) of 2,5-bis(chloromethyl)-3′-(3,7-dimethyloctyloxy) biphenyl and 1.63 g (3.9 mmol)of 2-methyl-5-(3,7-dimethyloctyl)-p-xylylene dibromide were dissolved in660 g of dehydrated 1,4-dioxane. The ratios of the monomers to the totalamount of the monomers were 8 mol %, 49 mol % and 43 mol %,respectively. The system was purged with nitrogen by bubbling nitrogenthrough this solution for 20 minutes, then, the solution was heated upto 95° C. under nitrogen atmosphere. To this solution was addeddropwise, over about 10 minutes, a solution prepared previously bydissolving 4.7 g of potassium t-butoxide in 80 g of dehydrated1,4-dioxane. After the addition, they were polymerized for 2.5 hours at97° C.

[0172] After the polymerization, the polymerized solution was cooled to50° C., then, neutralized by addition of acetic acid. After cooling toroom temperature, this polymerized solution was poured into 800 g ofmethanol, and the produced precipitate was recovered. This precipitatewas washed with ethanol, then, dried under reduced pressure. 1.5 g ofthe resulted polymer was dissolved in 400 g of THF. This solution waspoured into 800 g of methanol, and the produced precipitate wasrecovered. This precipitate was washed with ethanol, then, dried underreduced pressure to obtain 1.4 g of a polymer. This polymer is calledPolymer fluorescent substance 1. Polymer fluorescent substance 1 had anumber-average molecular weight of 2×10⁵.

[0173] <Fabrication of Device and Evaluation of Drift Mobility ofCarrier>

[0174] 0.006 g of Polymer fluorescent substance 1 was weighed, to thiswas added toluene to give 1 g of a mixture, and the mixture was stirredat room temperature to provide complete dissolution. This solution iscalled a toluene solution of Polymer fluorescent substance 1.

[0175] The toluene solution of Polymer fluorescent substance 1 obtainedabove was cast on a transparent conductive film formed on glass (ITO) toform a film having a thickness of 5.6 μm. Further, an Al electrode wasvapor-deposited on the thin film of Polymer fluorescent substance 1, andused as a sample for measuring the drift mobility of carrier. In thissample, positive voltage was applied to the transparent electrode forthis Al electrode, and a flush light (wavelength: 481 nm, flush time: 1nsec) was directed from the transparent electrode side by using anitrogen laser excitation type pigment laser, to measure the transitionlight current of hole. The hole drift mobility was calculated fromcurved point in log-log plot of time-transition light current. Likewise,negative voltage was applied to the transparent electrode for the Alelectrode, and a flush light was directed from the transparent electrodeside, to measure the transition light current of electron. The electrondrift mobility was calculated from curved point in log-log plot oftime-transition light current. As a result, at a measuring temperatureof 27° C. and an application voltage of 280 V (electric field: 0.5MV/cm), a hole drift mobility of 1.7×10⁻⁸ cm²/V/S was obtained, and atan application voltage of −280 V (electric field: 0.5 MV/cm), anelectron drift mobility of 2.4×10⁻⁸ cm²/V/s was obtained. The driftnobility ratio μ_(H)/μ_(E) was 0.71. Further, dependency of the holedrift mobility on filed intensity and temperature was measured at anelectric field of 0.3 to 1 MV/cm and a temperature of −5° C. to 40° C.At each temperature, E^(1/2) and log[μ (E, T)] were plotted using theresulted hole drift mobility μ (E, T) and electric field E, andapproximated linearly by the least square method, to obtain the value μ(E→0, T) of the section of the line. Then, 1/T2 and log[μ (E→0, T)] wereplotted, and approximated linearly by the least-square method, to give2×10⁻⁵ cm²/V/s, a value. of μ₀ from the section of the line.

[0176] <Fabrication of Device and Evaluation of Polymer LED Properties>

[0177] A suspension ofpoly(3,4)ethylenedioxythiophene/polystyrenesulfonic acid (Baytron P AI4083, manufactured by Bayer) was filtrated through a 0.5 μm membranefilter, then, spin-coated on a glass substrate carrying thereon an ITOfilm having a thickness of 150 nm formed by a sputtering method, to givea film having a thickness of 70 nm, and dried for 10 miniuts at 120° C.in an oven. Then, a light-emitting layer having a thickness of 70 nm wasformed by spin-coating a 0.6 wt %toluene solution of Polymer fluorescentsubstance 1 at room temperature. Further, this was dried for 1 hour at80° C. under reduced pressure, then, lithium fluoride was deposited togive a thickness of about 0.4 nm, then, calcium was deposited to give athickness of 40 nm, and aluminum was deposited to give a thickness of 70nm as a cathode, to fabricate a polymer LED device. The degrees ofvacuum in the depositions were all 8×10⁻⁶ Torr or less. When a voltageof 5.0 V was applied on the resulted device, a current of a currentdensity of 11.6 mA/cm² flowed, and EL light emission of yellow colorhaving a luminance of 680 cd/m² was observed. In this operation, thelight emission efficiency was 5.8 cd/A and the light emission spectrumof the device had a peak at 558 nm. The device was aged at a constantcurrent of 25 mA/cm² for 1 hour under nitrogen flow, then, drivencontinuously at a constant current of 25 mA/cm² under nitrogen flow. Asa result, a luminance of 700 cd/m² lowered to the half value over about470 hours.

Reference Example 1

[0178] <Synthesis of Polymer Fluorescent Substance 2>

[0179] 2.3 g of 2-methoxy-5-(2-ethylhexyloxy)-p-xylylene was dissolvedin 400 g of dehydrated 1,4-dioxane. The system was purged with nitrogenby bubbling nitrogen through this solution for 20 minutes. To thissolution was added dropwise, over about 30 minutes, a solution preparedpreviously by dissolving 4.7 g of potassium t-butoxide in 70 ml ofdehydrated 1,4-dioxane. After the addition, they were polymerized bymaintaining at room temperature for 15 hours.

[0180] After the polymerization, the polymerized solution wasneutralized by addition of acetic acid. This polymerized solution waspoured into 800 g of methanol, and the produced precipitate wasrecovered. This precipitate was washed with methanol, then, dried underreduced pressure to obtain 0.8 g of a polymer. This polymer is calledPolymer fluorescent substance 2. Polymer fluorescent substance 2 had anumber-average molecular weight of 1×10⁵.

Comparative Example 1

[0181] <Fabrication of Device and Evaluation of Drift Mobility ofCarrier>

[0182] 0.006 g of Polymer fluorescent substance 2 was weighed, to thiswas added toluene to give 1 g of a mixture, and the mixture was stirredat room temperature to provide incomplete dissolution. The mixture wasdissolved completely by stirring at 80° C., however, when the solutionwas cooled to room temperature, it showed gelling, meaning poorersolubility into toluene as compared with Polymer fluorescentsubstance 1. 0.004 g of Polymer fluorescent substance 2 was weighed, tothis was added chloroform to give 1 g of a mixture, and the mixture wasstirred at room temperature to provide complete dissolution, giving a0.4 wt % chloroform solution.

[0183] A thin film of Polymer fluorescent substance 2 having a thicknessof 3.3 μm was formed in the same manner as in Example 1 except by usingchloroform solution, and an Al electrode was deposited and used as asample for measurement of drift mobility. In this sample, positivevoltage or negative voltage was applied to the transparent electrode forthis Al electrode, and a flush light was directed from the transparentelectrode side, to measure the transition light current of hole andelectron. As a result, at a measuring temperature of 27° C. and anapplied voltage of 165 V (electric field: 0.5 MV/cm), a hole driftmobility of 4×10⁻⁶ cm²/V/s was obtained. When negative voltage wasapplied, in transition light log-log plot, curved point was not foundduring time range wherein an electron drift mobility of 1×10⁻⁷ cm²/V/sor more was obtained, and the electron drift mobility was estimated to1×10⁻⁷ cm²/V/s or less. In this case, the drift mobility ratioμ_(H)/μ_(E) ratio was estimated to 40 or more.

[0184] Further, dependency of the hole drift mobility on electric fieldand temperature was measured at an electric field of 0.3 to 1 MV/cm anda temperature of −10° C. to 40° C. At each temperature, E^(1/2) andlog[μ (E, T)] were plotted using the resulted hole drift mobility μ (E,T) and electric field E, and approximated linearly by the least-squaremethod, to obtain the value μ (E→0, T) of the section of the line. Then,1/T² and log[μ (E→0, T)] were plotted, and approximated linearly by theleast-square method, to give 7×10⁻⁴ cm²/V/s, a value of μ₀ from thesection of the line.

[0185] <Fabrication of Device and Evaluation of Polymer LED Properties>

[0186] A polymer LED device was produced at room temperature using thechloroform solution of Polymer fluorescent substance 2 by the samemanner as in Example 1. When a voltage of 3.2 V was applied on theresulted device, a current of a current density of 11 mA/cm² flowed, andEL light emission of orange color having a luminance of 129 cd/m² wasobserved. In this operation, the light emission efficiency was 1.1 cd/A.

Reference Example 2 <Synthesis of Polymer Fluorescent Substance 3>

[0187] 0.2 g (0.60 mmol) of 2-methoxy-5-(2-ethylhexyloxy)-p-xylylenedichloride and 12 g (29.5 mmol) of 2,5-bis(chloromethyl)-4′-(3,7-dimethyloctyloxy) biphenyl were dissolved in 2100g of dehydrated 1,4-dioxane. The ratios of the monomers to the totalamount of the monomers were 2 mol %, and 98 mol %, respectively. Thesystem was purged with nitrogen by bubbling nitrogen through thissolution for 20 minutes, then, the solution was heated up to 95° C.under nitrogen atmosphere. To this solution was added dropwise, overabout 10 minutes, a solution prepared previously by dissolving 15.5 g ofpotassium t-butoxide in 210 g of dehydrated 1,4-dioxane. After theaddition, they were polymerized by maintaining at 97° C. for 2.5 hours.

[0188] After the polymerization, the polymerized solution was cooled to50° C., then, neutralized by addition of acetic acid. After cooling toroom temperature, this polymerized solution was poured into 2500 g ofdeionized water, and the produced precipitate was recovered. Thisprecipitate was washed with methanol, then, dried under reducedpressure. 7 g of the resulted polymer was dissolved in 1500 g of THF.This solution was poured into 2000 g of methanol, and the producedprecipitate was recovered. This precipitate was washed with ethanol,then, dried under reduced pressure to obtain 5 g of a polymer. Thispolymer is called Polymer fluorescent substance 3. Polymer fluorescentsubstance 3 had a number-average molecular weight of 4×10⁵.

Comparative Example 2

[0189] 0.006 g of Polymer fluorescent substance 3 was weighed, to thiswas added toluene to give 1 g of a mixture, and the mixture was stirredat room temperature to provide incomplete dissolution. The mixture wasdissolved completely by stirring at 80° C., however, when the solutionwas cooled to room temperature, it showed gelling, meaning poorersolubility into toluene as compared with Polymer fluorescentsubstance 1. 0.004 g of Polymer fluorescent substance 3 was weighed, tothis was added chloroform to give 1 g of a mixture, and the mixture wasstirred at room temperature to provide complete dissolution, giving a0.4 wt % chloroform solution.

[0190] A polymer LED was produced using the chloroform solution ofPolymer fluorescent substance 3 instead of the toluene solution ofPolymer fluorescent substance 1 in the same manner as in Example 1. Whena voltage of 5.0 V was applied on the resulted device, a current of acurrent density of 3.9 mA/cm² flowed, and EL light emission of yellowcolor having a luminance of 320 cd/m² was observed. In this operation,the light emission efficiency was 8.3 cd/A and the light emissionspectrum of the device had a peak at 543, nm. The device was aged at aconstant current of 25 mA/cm² for 1 hour under nitrogen flow, then,driven continuously at a constant current of 25 mA/cm² under nitrogenflow. As a result, a luminance of 1200 cd/m² lowered to the half valueover about 43 hours.

Reference Synthesis Example 3

[0191] <Synthesis of 1,4-bis(bromomethyl)-2-(dimethyloctylsilyl)benzene>

[0192] 1.95 g (80.2 mmol) of finely cut magnesium metal was placed in a200 ml four-necked flask, and 50 ml of anhydrous tetrahydrofuran wasfurther charged. The mixture was heated up to 70° C. while stirring, and50 ml of a solution of 5 g (27.0 mmol) of 2-bromo p-xylene in anhydroustetrahydrofuran was added dropwise while caring for steep reaction(reflux). After completion of the addition, it was refluxed for 30minutes, then, cooled to 40° C., and to this was added 6.7 g (32.4 mmol)of dimethyloctylsilyl chloride while stirring. The solution was againheated and refluxed for 3 hours. The reaction mixture was charged in anaqueous saturated ammonium chloride solution, and extracted(toluene/water) and the organic phase was dried over sodium sulfate.After concentration, the product was purified and isolated by silica gelcolumn chromatography (n-hexane) to obtain 3.19 g of2-(dimethyloctylsilyl)-p-xylene.

[0193] 2 g (7.2 mmol) of 2-(dimethyloctylsilyl)-p-xylene was dissolvedin 50 ml of carbon tetrachloride, and 2.67 g (15.0 mmol) ofN-bromosuccinimide was charged into this while stirring. The mixture wasrefluxed for 5 hours, and after completion of the reaction, thedeposited solid was removed by filtrated, and to the filtrate was addedchloroform and the solution was washed with water, and the organic phasewas dried over sodium sulfate and concentrated. The product was purifiedand isolated by silica gel column chromatography (n-hexane) to obtain1.4 g of 1,4-bis (bromomethyl)-2-(dimethyloctylsilyl)benzene.

Example 2

[0194] <Synthesis of Polymer Fluorescent Substance 4>

[0195] 0.41 g (1.0 mmol) of 1,4-bis(chloromethyl)-2-{4′-(3,7-dimethyloctyloxy) phenyl}benzeneando.368 g(0.86 mmol) of 1,4-bis(bromomethyl)-2-(dimethyloctylsilyl)benzene and0.0533 g (0.16 mmol) of 2-methoxy-5-(2-ethylhexyloxy)-p-xylylenedichloride were dissolved in 200 g of 1,4-dioxane (dehydrated). Theratios of the monomers to the total amount of the monomers were 49 mol%, 43 mol % and 8 mol %, respectively.

[0196] The system was purged with nitrogen by bubbling nitrogen throughthis solution for 20 minutes, then, the solution was heated up to 95° C.under nitrogen atmosphere. To this solution was added dropwise, overabout 10 minutes, a solution prepared previously by dissolving 1.1 g ofpotassium t-butoxide in 30 ml of 1,4-dioxane (dehydrated) and bybabbling a nitrogen gas for nitrogen purge. After the addition, theywere subsequently polymerized for 2.5 hours at 95° C. The reaction wasconducted in a nitrogen gas atmosphere.

[0197] Then, this solution was cooled, then, neutralized by addition ofacetic acid. Methanol was added to this solution, and the producedprecipitate was recovered. This precipitate was washed with ethanol,then, dried under reduced pressure to obtain 0.39 g of a polymer. Then,this precipitate was dissolved in about 110 g of THF, and againprecipitated and purified by adding methanol to the solution. Theresulted precipitate was washed with ethanol, then, dried under reducedpressure to obtain 0.36 g of a polymer. The resulted polymer is calledPolymer fluorescent substance 4.

[0198] Polymer fluorescent substance 4 had a number-average molecularweight in terms of polystyrene of 9.3×10⁴.

[0199] <Fabrication of Device and Evaluation of Polymer LED Properties>

[0200] 0.0067 g of Polymer fluorescent substance 4 was weighed, to thiswas added toluene to give 1 g of a mixture, and the mixture was stirredat room temperature to provide complete dissolution. This solution iscalled a toluene solution of Polymer fluorescent substance 4.

[0201] A polymer LED device was fabricated at room temperature using thetoluene solution of Polymer fluorescent substance 4 by the same manneras in Example 1. When a voltage of 4.0 V was applied on the resulteddevice, a current of a current density of 8.1 mA/cm² flowed, and ELlight emission of yellow color having a luminance of 272 cd/M² wasobserved. In this operation, the light emission efficiency was 3.4 cd/Aand the light emission spectrum of the device had a peak at 564 nm. Thedevice was aged at a constant current of 25 mA/cm² for 1 hour undernitrogen flow, then, driven continuously at a constant current of 25mA/cm² under nitrogen flow. As a result, the half-life was 230 hours.

Example 3

[0202] <Synthesis of Polymer Fluorescent Substance 5>

[0203] 0.41 g (1.0 mmol) of 1,4-bis(chloromethyl)-2-{4′-(3,7-dimethyloctyloxy)phenyl}benzene and 0.184 g(0.43 mmol) of 1,4-bis(bromomethyl)-2-(dimethyloctylsilyl)benzene, 0.18g (0.43 mmol) of 2-methyl-5-(3,7-dimethyloctyl)-p-xylylene dibromide and0.0533 g (0.16 mmol) of 2-methoxy-5-(2-ethylhexyloxy)-p-xylylenedichloride were dissolved in 200 g of 1,4-dioxane (dehydrated). Theratios of the monomers to the total amount of the monomers were 50 mol%, 21 mol %, 21 mol % and 8 mol %, respectively. The system was purgedwith nitrogen by bubbling nitrogen through this solution for 20 minutes,then, the solution was heated up to 95° C. under nitrogen atmosphere. Tothis solution was added dropwise, over about 10 minutes, a solutionprepared previously by dissolving 1.1 g of potassium t-butoxide in 30 mlof 1,4-dioxane (dehydrated) and by babbling a nitrogen gas for nitrogenpurge. After the addition, they were subsequently polymerized for 2hours at 95° C. The reaction was conducted in a nitrogen gas atmosphere.

[0204] Then, this solution was cooled, then, neutralized by addition ofacetic acid. Methanol was added to this solution, and the producedprecipitate was recovered. This precipitate was washed with ethanol,then, dried under reduced pressure to obtain 0.40 g of a polymer. Then,this precipitate was dissolved in about 120 g of THF, and againprecipitated and purified by adding methanol to the solution. Theresulted precipitate was washed with ethanol, then, dried under reducedpressure to obtain 0.36 g of a polymer. The resulted polymer is calledPolymer fluorescent substance 5.

[0205] Polymer fluorescent substance 5 had a number-average molecularweight in terms of polystyrene of 1.2×10⁵.

[0206] <Production and Evaluation of Device>

[0207] 0.0074 g of Polymer fluorescent substance 5 was weighed, to thiswas added toluene to give 1 g of a mixture, and the mixture was stirredat room temperature to provide complete dissolution. This solution iscalled a toluene solution of Polymer fluorescent substance 5.

[0208] A polymer LED device was fabricated using the toluene solution ofPolymer fluorescent substance 5 by the same manner as in Example 1. Whena voltage of 4.0 V was applied on the resulted device, a current of acurrent density of 5.6 MA/cm² flowed, and EL light emission of yellowcolor having a luminance of 377 cd/m² was observed. In this operation,the light emission efficiency was 6.7 cd/A and the light emissionspectrum of the device had a peak at 560 nm. The device was aged at aconstant current of 25 mA/cm² for 1 hour under nitrogen flow, then,driven continuously at a constant current of 25 mA/cm² under nitrogenflow. As a result, the half-life was 250 hours.

[0209] A polymer fluorescent substance of the present invention has moreexcellent solubility into an organic solvent, and when it is used for apolymer LED, higher efficiency and longer life are obtained. Therefore,this polymer LED can be preferably used as a back light of a curved orsheet light source, as a display device of segment type, in apparatusessuch as a flat panel display of dot matrix type, and the like.

What is claimed is:
 1. A polymer fluorescent substance which emitsfluorescence in solid state, has a number-average molecular weight interms of polystyrene of 1×10⁴ to 1×10⁸, has at least one repeating unitof the following general formula (1) and in which the ratio of the holedrift mobility μ_(H) to the electron drift mobility μ_(E) of saidpolymer fluorescent substance is from 0.1 to 10:

[in the formula, Ar₁ is a divalent group forming carbon-carbon bondswith adjacent two groups respectively, the divalent group being anarylene group having 6 to 60 carbon atoms participating in conjugationor a heterocyclic compound group having 3 to 60 carbon atomsparticipating in conjugation, and the arylene group and heterocycliccompound group may further have a substituent. Each of R₁ and R₂independently represents a group selected from the group consisting of ahydrogen atom, linear, branched or cyclic alkyl groups having 1 to 20carbon atoms, aryl groups having 6 to 60 carbon atoms, heterocycliccompound groups having 3 to 60 carbon atoms and a cyano group, and thearyl group and heterocyclic compound group may further have asubstituent. The symbol j is 0 or 1.].
 2. The polymer fluorescentsubstance according to claim 1 wherein the hole drift mobility withoutenergetic disorder and spatial disorder is 5×10⁻⁴ cm²/V/s or less.
 3. Apolymer fluorescent substance which emits fluorescence in solid state,has a number-average molecular weight in terms of polystyrene of 1×10⁴to 1×10⁸, and has each of the repeating units represented by repeatingunits of the formulae (2), (3) and (4):

[in the formula, Ar₂ is an arylene group having 6 to 60 carbon atomscontained in the main chain portion or a divalent heterocyclic compoundgroup having 3 to 60 carbon atoms contained in the main chain portion. Xrepresents an oxygen atom or sulfur atom. R₃ represents a group selectedfrom the group consisting of linear, branched or cyclic alkyl groupshaving 1 to 20 carbon atoms, mono, di or trialkylsilyl groups having 1to 60 carbon atoms, aryl groups having 6 to 60 carbon atoms, arylalkylgroups having 7 to 60 carbon atoms and heterocyclic compound groupshaving 3 to 60 carbon atoms, and the aryl group, arylalkyl group andheterocyclic group may also have a substituent. The symbol k is aninteger from 1 to
 4. Each of R₄ and R₅ independently represents a groupselected from the group consisting of a hydrogen atom, linear, branchedor cyclic alkyl groups having 1 to 20 carbon atoms, aryl groups having 6to 60 carbon atoms, heterocyclic compound groups having 3 to 60 carbonatoms and a cyano group, and the aryl group and heterocyclic group mayalso have a substituent. The symbol m is 0 or
 1. Ar₂ may have asubstituent selected from the group consisting of linear, branched orcyclic alkyl groups having 1 to 20 carbon atoms, mono, di ortrialkylsilyl groups having 1 to 60 carbon atoms, mono or dialkylaminogroups having 1 to 40 carbon atoms, aryl groups having 6 to 60 carbonatoms, arylalkyl groups having 7 to 60 carbon atoms, arylamino groupshaving 6 to 60 carbon atoms, heterocyclic compound groups having 3 to 60carbon atoms and a cyano group, and the aryl group, arylalkyl group,arylamino group and heterocyclic group may further have a substituent.When Ar₂ has a plurality of substituents, they may be the same ordifferent. One or more carbon atoms of the substituent on Ar₂ may besubstituted with an oxygen atom or sulfur atom, and one or more hydrogenatoms of the substituent on Ar₂ may be substituted with a fluorineatom.],

(in the formula, Ar₃ is an arylene group having 6 to 60 carbon atomscontained in the main chain portion or a heterocyclic compound grouphaving 3 to 60 carbon atoms contained in the main chain portion. Ar₄ isan aryl group having 6 to 60 carbon atoms or a heterocyclic compoundgroup having 3 to 60 carbon atoms, and may also have a substituentselected from the group consisting of linear, branched or cyclic alkylgroups having 1 to 20 carbon atoms, alkoxy groups having a linear,branched or cyclic alkyl group having 1 to 20 carbon atoms, alkylthiogroups having a linear, branched or cyclic alkyl group having 1 to 20carbon atoms, mono, di or trialkylsilyl groups having 1 to 60 carbonatoms, mono or dialkylamino groups having 1 to 40 carbon atoms, arylgroups having 6 to 60 carbon atoms, aryloxy groups having 6 to 60 carbonatoms, arylalkyl groups having 7 to 60 carbon atoms, arylalkoxy groupshaving 7 to 60 carbon atoms, arylalkenyl groups having 8 to 60 carbonatoms, arylalkynyl groups having 8 to 60 carbon atoms, arylamino groupshaving 6 to 60 carbon atoms, heterocyclic compound groups having 3 to 60carbon atoms and a cyano group, and the aryl group, aryloxy group,arylalkyl group, arylalkoxy group, arylalkenyl group, arylalkynyl group,arylamino group and heterocyclic group may further have a substituent.The symbol n is an integer from 1 to
 4. Each of R₆ and R₇ independentlyrepresents a group selected from the group consisting of a hydrogenatom, linear, branched or cyclic alkyl groups having 1 to 20 carbonatoms, aryl groups having 6 to 60 carbon atoms, heterocyclic compoundgroups having 3 to 60 carbon atoms and a cyano group, and the aryl groupand heterocyclic group may also have a substituent. The symbol p is 0or
 1. Ar₃ may have a substituent selected from the group consisting oflinear, branched or cyclic alkyl groups having 1 to 20 carbon atoms,alkoxy groups having a linear, branched or cyclic alkyl group having 1to 20 carbon atoms, alkylthio groups having a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, mono, di or trialkylsilylgroups having 1 to 60 carbon atoms, mono or dialkylamino groups having 1to 40 carbon atoms, aryloxy groups having 6 to 60 carbon atoms,arylalkyl groups having 7 to 60 carbon atoms, arylalkoxy groups having 7to 60 carbon atoms, arylamino groups having 6 to 60 carbon atoms, and acyano group, and the aryloxy group, arylalkyl group, arylalkoxy group,arylamino group may further have a substituent. When Ar₃ has a pluralityof substituents, they may be the same or different. One or more carbonatoms of the substituents on Ar₃ may be substituted with an oxygen atomor sulfur atom, and one or more hydrogen atoms of the substituents onAr₃ maybe substituted with a fluorine atom.],

[in the formula, Ar₅ is an arylene group having 6 to 60 carbon atomscontained in the main chain portion or a divalent heterocyclic compoundgroup having 3 to 60 carbon atoms contained in the main chain portion.R₈ represents a group selected from the group consisting of linear,branched or cyclic alkyl groups having 1 to 20 carbon atoms, mono, di ortrialkylsilyl groups having 1 to 60 carbon atoms, mono or dialkylaminogroups having 1 to 40 carbon atoms, saturated heterocyclic compoundgroups having 3 to 60 carbon atoms and arylalkyl groups having 7 to 60carbon atoms, and the arylalkyl group may further have a substituent.The symbol q is an integer from 1 to
 4. Each of R₉ and R₁₀ independentlyrepresents a group selected from the group consisting of a hydrogenatom, linear, branched or cyclic alkyl groups having 1 to 20 carbonatoms, aryl groups having 6 to 60 carbon atoms, heterocyclic compoundgroups having 3 to 60 carbon atoms and a cyano group, and the aryl groupand heterocyclic group may also have a substituent. The symbol r is 0or
 1. Ar₅ may have a substituent selected from the group consisting ofalkoxy groups having a linear, branched or cyclic alkyl group having 1to 20 carbon atoms, alkylthio groups having a linear, branched or cyclicalkyl group having 1 to 20 carbon atoms, aryl groups having 6 to 60carbon atoms, aryloxy groups having 6 to 60 carbon atoms, arylalkoxygroups having 7 to 60 carbon atoms, arylamino groups having 6 to 60carbon atoms, heterocyclic compound groups having 3 to 60 carbon atomsand a cyano group, and the aryl group, aryloxy group, arylalkoxy group,arylamino group and heterocyclic group may further have a substituent.When Ar₅ has a plurality of substituents, they may be the same ordifferent. One or more carbon atoms of the substituents on Ar₅ may besubstituted with an oxygen atom or sulfur atom, and one or more hydrogenatoms of the substituents on Ar₅ may be substituted with a fluorineatom.].
 4. The polymer fluorescent substance according to claim 3,wherein, in the polymer fluorescent substance containing each one ormore repeating units of the formulae (2), (3) and (4) respectively, thetotal amount of repeating units of the formulae (2), (3) and (4) is 50mol % or more based on all repeating units, and the amount of repeatingunits of the formula (2) is 0.1 mol % to 30 mol %, the amount ofrepeating units of the formula (3) is 29.9 mol % to 70 mol % and theamount of repeating units of the formula (4) is 29.9 mol % to 70 mol %,based on the total amount of repeating units of the formulae (2), (3)and (4).
 5. The polymer fluorescent substance according to claim 3 or 4,wherein, in the formula (2), Ar₂ is an arylene group having 6 to 20carbon atoms contained in the main chain and X is an oxygen atom, in theformula (3), Ar₃ is an arylene group having 6 to 20 carbon atomscontained in the main chain, and in the formula (4), Ar₅ is an arylenegroup having 6 to 20 carbon atoms contained in the main chain.
 6. Thepolymer fluorescent substance according to any of claims 3 to 5,wherein, in the formula (4), R₈ is a mono, di or trialkylsilyl grouphaving 1 to 60 carbon atoms.
 7. The polymer fluorescent substanceaccording to any of claims 3 to 6, comprising at least four repeatingunits of the formulae (2), (3) and (4).
 8. The polymer fluorescentsubstance according to any of claims 3 to 7, wherein the ratio of thehole drift mobility H to the electron drift mobility μ_(E) is from 0.1to
 10. 9. The polymer fluorescent substance according to claim 8,wherein the hole drift mobility without energetic disorder and spatialdisorder is 5×10⁻⁴ cm²/V/s or less.
 10. A polymer light-emitting devicecomprising at least one light-emitting layer containing a polymerfluorescent substance, placed between a pair of an anode and a cathodeat least one of which is transparent or semi-transparent, wherein, thelight-emitting layer contains a polymer fluorescent substance accordingto any of claims 1 to
 9. 11. A sheet light source using a polymerlight-emitting device according to claim
 10. 12. A segment displayapparatus using a polymer light-emitting device according to claim 10.13. A dot matrix display apparatus using a polymer light-emitting deviceaccording to claim
 10. 14. A liquid crystal display apparatus using apolymer light-emitting device according to claim 10 as a back light.